Abstract: A digital electronic module arrangement includes a module rack carrying a plurality of individual modules which can each be plugged into the rack. A test rack is connected to the module for applying test signals to each module. The module can select either process inputs or test inputs. A testing device provided for individually testing module outputs which respond to a common input. Each module has a rear bus board which has a connector that can be plugged into the module rack, and a forward digital bus board. A window in the front panel allows direct viewing of indicia on a chip corresponding to code within the chip. This code is electronically compared to code in the module software which relates to the module function. A nameplate on the front panel carries the same indicia for ensuring visual verification that the correct function is attributed to the correct module. Electronic verification is also provided by equipment in the test rack.